As the aforementioned coating method, there is recently proposed a cold spray method, for example. This cold spray method is a process for forming a coating on a front surface of a substrate by use of a spray device arranged to discharge a jet of material powder (particles) at high velocities from a nozzle together with working gas heated to a temperature lower than a melting point or a softening temperature of the material powder, thereby causing the material powder in solid state impact or collide against the front surface of the substrate. This cold spray method does not need to heat the material powder to high temperatures as compared with a thermal spraying method in which material powder is sprayed in melted or softened state onto a front surface of a substrate at high velocities. Accordingly, it is possible to prevent the property of the material powder from deteriorating due to oxidization and others and hence to form a coating with high adhesion with respect to the front surface of the substrate.
The above cold spray method is disclosed in for example Patent Literature 1 listed below. In this cold spray method, as shown in FIG. 4, a heating plate 111 is connected to a back surface 110b of a substrate 110, and a heater 112 for heating the heating plate 111 is provided. Patent Literature 1 listed below also discloses a modified example in which a front surface 110a of the substrate 110 is heated by a laser. Accordingly, material powder (particles) 121 sprayed from a cold spray device 120 collides against the front surface 110a of the heated substrate 110. Due to this collision, the material powder 121 and the front surface 110a of the substrate 110 are deformed. As a result, an adhesion rate of the material powder 121 to the front surface 110a of the substrate 110 and adhesion strength thereof can be improved and further a coating 130 of the material powder 121 can be formed compactly.